A cylindrical hydrogen tank is housed under a floor tunnel, which is disposed at the center in a vehicle width direction of a floor panel along a vehicle front-back direction so as to protrude upward along a height direction, and includes a casing having a load bearing property. A seat cross member is disposed on a side of the hydrogen tank along the vehicle width direction. A seat pipe is joined to the seat cross member and disposed so as to extend along the vehicle width direction. The seat pipe and the seat cross member are arranged within the height of the hydrogen tank in a vehicle height direction, and also respectively located above and below the most outwardly protruded lateral end point in the vehicle width direction of the hydrogen tank.